How to Coat Corner Bead
Once corner bead is installed it is coated with drywall mud to create smooth outside corners. Generally a minimum of two coats of drywall compound is needed, however a third skim coat may sometimes be added to cover any final imperfections. The first coat of drywall compound is generally applied to corner bead following the taping step. Follow the process below learn how to coat drywall corner bead.
Various corner beads may be used. Metal bead installed with screws or drywall nails is very common however vinyl corner bead installed with spray adhesive is also common. The pictures displayed here show vinyl corner bead used on green board (moisture resistant drywall panels). Metal corner bead with paper tape on the edges is used at times. The tape is applied to the drywall with drywall compound using a process similar to that involved in taping drywall seams. Follow this link to see how to tape drywall seams using paper tape.
Using an eight or ten inch drywall knife, spread drywall compound evenly on the drywall near the corner bead. The knife should run against the bead as a guide. Don’t allow the knife to pull away from the bead. The mud should be evenly dispersed across and under the knife. Notice how the two fingers are pressed against the mid section of the drywall knife. This helps to ensure even pressure and control when applying mud. Start applying mud from the top of the corner bead pulling down.
Spread drywall mud from the bottom of the bead pulling up and into the mud applied in Step 2. Subsequent applications of drywall mud should be pulled into mud already on the wall rather than pulling away from mud on the wall. Therefore, mud should be applied to the bead from the center toward the two ends. This helps to keep the thickness of the mud even throughout.
Using heavy pressure on one side of the knife, clean the outside edge of mud applied on the wall. Notice how one finger is placed to the left of the handle on the drywall knife in the picture. This aids in placing pressure where needed. The right hand side of the drywall mud is guided by the corner bead and therefore does not need to be cleaned in this way, only the area where the mud tapers into the drywall.
Once drywall mud is evenly applied along the length of the corner bead and the edge has been tapered into the drywall, run the knife along the entire length of the corner bead using even pressure. The right side of the knife should run along the corner bead as a guide while the left side should run along the drywall. This step smoothes the surface of the mud just applied. Try not to remove too much mud in this step. Use only enough pressure to smooth the mud. Too much pressure will remove too much mud and leave the corner bead hollow and concaved.
Once the mud has dried, repeat the process above using a larger drywall knife. If you used an eight inch knife on the first coat, use a ten inch on the second coat. If you used a ten inch knife on the first coat, use a twelve inch knife on the second coat. At times a third very thin coat is needed to cover any residual imperfections.